Local magnetic properties around a nonmagnetic impurity are investigated in high-Tc cuprate superconductors. We consider a model two-dimensional dx2−y2-wave superconductor with strong antiferromagnetic (AF) spin fluctuations and calculate the spin susceptibility around the impurity. We show that the uniform susceptibility (χ(0)), which is usually suppressed in spin-singlet superconductivity, is...

We review our recent measurements of the complex AC conductivity of thin InOx films studied as a function of magnetic field through the nominal 2D superconductor-insulator transition. These measurements the first of their type to probe nonzero frequency reveals a significant finite frequency superfluid stiffness well into the insulating regime. Unlike conventional fluctuation superconductivity ...

beta-YbAlB4 is the first Yb-based heavy fermion superconductor with Tc = 80 mK. Our study using high-purity single crystals reveals that strongly type-II heavy fermion superconductivity emerges from the non-Fermi-liquid state with enhanced ferromagnetic fluctuations. High sensitivity of Tc to sample purity indicates strong pair-breaking effects due to impurities, probably of nonmagnetic type, s...

Numerical simulations of conduction through a disordered microbridge between a normal metal and a superconductor have revealed an anomalous insensitivity of the conductance fluctuations to a magnetic field. A theory for the anomaly is presented: Both an exact analytical calculation (using randommatrix theory) and a qualitative symmetry argument (involving the exchange of time-reversal for refle...

Chiral order of the Josephson-junction ladder with half a flux quantum per plaquette is studied by means of the exact diagonalization method. We consider an extreme quantum limit where each superconductor grain (order parameter) is represented by S = 1/2 spin. So far, the semi-classical S → ∞ case, where each spin reduces to a plane rotator, has been considered extensively. We found that in the...

It is shown through detailed inelastic neutron scattering experiments that the gapped collective magnetic excitation of the unconventional superconductor CeCoIn5, the spin resonance mode, is incommensurate and that the corresponding fluctuations are of an Ising nature. The incommensurate peak position of these fluctuations corresponds to the propagation vector of the adjacent field induced stat...

Recent experiments have shown that the superconducting energy gap in some cuprates is spatially inhomogeneous. Motivated by these experiments, and using exact diagonalization of a model d-wave Hamiltonian, combined with Monte Carlo simulations of a Ginzburg-Landau free energy functional, we have calculated the single-particle local density of states LDOS ,r of a model high-Tc superconductor as ...

The Bose Metal: gauge field fluctuations and scaling for field tuned quantum phase transitions Abstract In this paper, we extend our previous discussion of the Bose metal to the field tuned case. We point out that the recent observation of the metallic state as an intermediate phase between the superconductor and the insulator in the field tuned experiments on MoGe films is in perfect consisten...